Dye diffusion transfer film containing alkali-dissociable inorganic salts

ABSTRACT

Integral negative-positive film units adapted for forming multicolor transfer images, which film units include A NEGATIVE COMPONENT COMPRISING A BLUE-SENSITIVE, A GREENSENSITIVE AND A RED-SENSITIVE GELATINO SILVER HALIDE EMULSION HAVING ASSOCIATED THEREWITH IN A CONTIGUOUS LAYER, RESPECTIVELY, A YELLOW DYE DEVELOPER, A MAGENTA DYE DEVELOPER AND A CYAN DYE DEVELOPER, AT LEAST ONE SET OF SAID EMULSION LAYERS AND ASSOCIATED DYE DEVELOPER LAYERS BEING SEPARATED FROM ANOTHER SET OF EMULSION LAYERS AND ASSOCIATED DYE DEVELOPER LAYERS BY AN INTERLAYER COMPRISING A DYE IMPERMEABLE COALESCED ESSENCE OF AN AQUEOUS FILM-FORMING POLYMER DISPERSION AND A PROCESSING COMPOSITION PERMEABLE MATERIAL ASSOCIATED THEREWITH AND ADAPTED TO RENDER THE INTERLAYER PERMEABLE TO SOLUBILIZED DYE IMAGEFORMING MATERIAL SUBSEQUENT TO BEING CONTACTED WITH AN AQUEOUS ALKALINE PROCESSING COMPOSITION; A POSITIVE COMPONENT INCLUDING A LEAST A DYEABLE STRATUM AND PREFERABLY ALSO A PH-reducing layer; and MEANS FOR PROVIDING A REFLECTING LAYER BETWEEN THE POSITIVE AND NEGATIVE COMPONENTS SO THAT A MULTICOLOR TRANSFER IMAGE IMPARTED TO THE DYEABLE STRATUM MAY BE VIEWED AS A REFLECTION PRINT WITHOUT SEPARATION OF THE POSITIVE AND NEGATIVE COMPONENT, WHICH MEANS MAY COMPRISE A PREFORMED LAYER DISPOSED BETWEEN THE NEGATIVE AND POSITIVE COMPONENTS OR A REAGENT OR COMBINATION OF REAGENTS TO BE APPLIED TO THE EXPOSED FILM UNIT TO PROVIDE THE REFLECTING LAYER; WHEREIN AT LEAST THE COATING SOLUTION EMPLOYED TO PROVIDE A SILVER HALIDE EMULSION LAYER CONTIGUOUS WITH SAID INTERLAYER INCLUDES AN ALKALI-DISSOCIABLE INORGANIC SALT TO OBTAIN GREATER TRANSFER OF THE ASSOCIATED DYE TO THE POSITIVE COMPONENT IN TERMS OF THE EXPOSED AREAS OF THE ASSOCIATED SILVER HALIDE LAYER.

"United States Patent [191 Barstow et a1.

1 1 DYE DIFFUSION TRANSFER FILM CONTAINING ALKALl-DISSOCIABLE vINORGANIC SALTS [75] Inventors: Frederick C. Barstow, Concord;

Carole .1. Uhrich, Belmont, both of Mass.

[73] Assignee: Polaroid Corporation, Cambridge,

Mass.

[22] Filed: Jan. 10, 1972 [21] Appl. No.: 216,717

[52] US. Cl 96/77, 96/3, 96/29 D, 96/108 [51] Int. Cl. G03c 1/40, G03c 7/00, G036 5/54, G03c H28 [58] Field of Search 96/77, 3, 29 D, 108, 110

[56] References Cited UNITED STATES PATENTS 2,839,405 I 6/1958 Jones 96/108 3,239,336 3/1966 Rogers et a1.... 96/77 3,249,432 5/1966 Haas 96/77 3,290,148 12/1966 Reid. 96/66 R 3,415,644 12/1968 Land 96/29 D 3,482,972 12/1969 1de1son.... 96/29 D 3,563,739 2/1971 1delson.... 96/29 D 3,597,200 8/1971 ldelson 96/29 D 3,625,685 12/1971 Avtges et a1. 96/29 D 3,705,798 12/1972 Kliem et a1. 96/3 Primary ExaminerRonald H. Smith Assistant Examiner-Richard Schilling [5 7] ABSTRACT Integral negative-positive film units adapted for form- June 25, 1974 lng multicolor transfer images, which film units include a negative component comprising a blue-sensitive, a green-sensitive and a red-sensitive gelatino silver halide emulsion having associated therewith in a contiguous layer, respectively, a yellow dye developer, at magenta dye developer and a cyan dye developer, at least one set of said emulsion layers and associated dye developer layers being separated from another set of emulsion layers and associated dye developer layers by an interlayer comprising a dye impermeable coalesced essence of an aqueous film-forming polymer dispersion and a processing composition permeable material associated therewith and adapted to render the -interlayer permeable to solubilized dye image-forming material subsequent to being contacted with an aqueous alkaline processing composition;

a positive component including a least a dyeable stratum and preferably also a pl-l-reducing layer; and

means for providing a reflecting layer between the positive and negative components so that a multicolor transfer image imparted to the dyeable stratum may be viewed as a reflection print without separation of the positive and negative component, which means may comprise a preformed layer disposed between the negative and positive components or a reagent or combination of reagents to be applied to the exposed film unit to provide the reflecting layer;

wherein at least the coating solution employed to provide a silver halide emulsion layer contiguous with said interlayer includes an alkali-dissociable inorganic salt to obtain greater transfer of the associated dye to the positive component in terms of the exposed areas of the associated silver halide layer.

' 20 Claims, No Drawings DYE DIFFUSION TRANSFER FILM CONTAINING ALKALI-DISSOCIABLE INORGANIC SALTS BACKGROUND OF THE INVENTION US. Pat. No. 2,983,606 discloses color diffusion transfer systems employing dye developers (dyes which are also silver halide developing agents) as the dye image-providing material. While many dye developers useful in these color diffusion transfer systems have heretofore been disclosed in the literature, of particular interest in the practice of the present invention are the phthalocyanine cyan dye developers of the type described in US. Pat. No. 3,482,972; the 1:1 chromecomplexed azo magenta dye developers of the type described in US. Pat. Nos. 3,563,739 and 3,551,406; and the 1:1 chrome-complexed azomethine yellow dye developers of the type described in US. Pat. No. 3,597,200. These dye developers will be described with more particularity hereinafter.

Film units employing a negative component includ' ing at least one light-sensitive silver halide layer having a dye image-providing material, e.g., a dye developer associated therewith and a positive component including at least a dyeable stratum to obtain in the positive component, upon exposure and development of the thus exposed film unit, a color transfer image which is viewable without separation of the respective components as a positive print, are also known and are described, for example, in US. Pat. Nos. 3,4l5,644; 3,415,645; 3,415,646; 3,473,925; 3,573,042; 3,573,043; 3,573,044; 3,576,625; 3,576,626; 3,578,540; 3,579,333; 3,594,l64; 3,594,165 and others. In such film units the positive and negative components are laminated and/or otherwise retained in superposition by physical means, such as a binding tape, the essential layers comprising the two components being contained either on a single support member or confined between a pair of support members. Where a support member is associated with the positive component where the color image is to be formed, it will be appreciated that at least this support member should be transparent to permit viewing therethrough of the color transfer image. In addition to the aforementioned essential layers, such film units further include means for providing a reflecting layer, most preferably a white reflecting layer, between the dyeable stratum of the positive component and the negative component in order to mask effectively the silver image or images formed as a function of development and any associated dye image-providing material remaining after development and transfer image formation and to provide a background for viewing the color image so formed in the dyeable stratum, without separation, by reflected light, as is disclosed in the various patents mentioned above. This reflecting layer which may, for example, comprise a white pigment such as titancium dioxide, may be present as a preformed layer included in the essential layers of the film unit or the reflecting agent may be provided after photoexposure, e.g., by including the reflecting agent in the processing composition. The film unit may also contain other layers performing specific desired functions, e.g., spacer layers, barrier layers, neutralizing layers, etc. In a particularly preferred form, these film units are employed in conjunction with a rupturable container of known description containing the requisite processing composition and adapted, upon application of compressive pressure, of applying its contents to develop the exposed film unit, e.g., by applying the processing composition in a substantially uniform layer between the dyeable stratum and the negative component.

Multicolor images may be obtained by employing a negative component including at least two selectively sensitized silver'halide layers, the most common such structure being the so-called tripack construction employing a red-sensitive, a green-sensitive and a bluesensitive gelatino silver halide emulsion layer having associated therewith, respectively, a cyan, a magenta and a yellow dye image-providing material. As is described and claimed in the copending application of Kliem et al., Ser. No. 78,408 filed Oct. 6, 1970 and now US. Pat. No. 3,705,798, these silver halide emulsion layers (as well as any other gelatin-containing layers) may also include an anionic polymeric material such as polyvinyl hydrogen phthalate (PVHP) to obtain certain distinct advantages, including greater dye transfer densities and faster diffusion rates.

It is known to provide an interlayer between each set of silver halide emulsion layers and associated dye developer layer in order to prevent interimage effects resulting in a loss of color purity or fidelity of the resulting color transfer image. The problems of back diffusion' and interimage effects are described more fully in the patent literature relating to the use of such negative interlayers" and need not be described in more detail herein. One such class of negative interlayers of use in integral negative-positive film units and to which this invention is directed are those described and claimed in US. Pat. No. 3,625,685. These interlayers, which comprise a dye permeable coalesced essence of an aqueous film-forming polymer dispersion and a processing composition permeable material associated therewith and adapted to render the interlayer permeable to solubilized dye image-forming material subsequent to being contacted with the processing composition, will be described in more detail hereinafter.

In the integral negative-positive film units contemplated by this invention, opacifying means may be pro vided on either side of the negative component so that the film unit may be processed in the light to provide the desired color transfer image. In a particularly useful embodiment such opacifying means may comprise an opaque dimensionally stable layer or support member positioned on the free or outer surface of the negative component, i.e., on the surface of the film unit opposed from the positive component containing the dyeable stratum, to prevent photoexposure by actinic light incident thereon from this side of the film unit and an opacifying agent applied during development between the dyeable stratum and the negative component, e.g., by including the opacifying agent in a developing composition so applied in order to prevent further exposure (fogging) by actinic light incident thereon from the other side of the film unit when the thus exposed film unit is developed in the light. The last mentioned opacifying agent may comprise the aforementioned reflecting agent which masks the negative component and provides the requisite background for viewing the transfer image formed thereover. Where this reflecting agent is insufficient to provide the requisite opacity, it may be employed in combination with an additional opacifying agent in order to prevent further exposure of the light-sensitive silver halide layer or layers by actinic light incident thereon.

In general these film units may be exposed to form a developable image and thereafter developed by applying the appropriate processing composition to develop exposed silver halide and to form, as a function of development, an imagewise distribution of diffusible dye image-providing material which is then transferred, at least in part, by diffusion to the dyeable stratum to impart thereto the desired color transfer image. As was heretofore mentioned, common to all of these systems in the provision of a reflecting layer between the dyeable stratum and the photosensitive strata to mask effectively the latter and to provide a background for viewing the color image imparted to the dyeable stratum, whereby this image may be viewed, by reflected light, without separation from the other layers or elements of the film unit.

A preferred opacification system to be contained in the processing composition is that described in the copending applications of Edwin H. Land, Ser. No. 43,782, filed June 5, 1970 and now abandoned, and Ser. No. 101,968, filed Dec. 28, 1970 and now U.S. Pat. No. 3,647,437, comprising an inorganic reflecting pigment dispersion containing at least one optical filter agent at a pH above the pKa of the optical filter agent in a concentration effective, when the processing composition is applied, to provide a layer exhibiting optical transmission density than about 6.0 density units with respect to incident radiation actinic to the photosensitive silver halide layer and optical reflection density than about 1.0 density with respect to incident visible radiation.

In lieu of having the reflecting pigment contained in the processing composition, e.g., as disclosed in the above-mentioned copending applications, the reflecting pigment needed to mask the photosensitive strata and to provide the requisite background for viewing the color transfer image formed in the receiving layer may be contained initially in whole or in part as a preformed layer in the film unit. As an example of such a preformed layer, mention may be made of that disclosed on the copending applications of Edwin H. Land, Ser. Nos. 846,441, filed July 31, 1969, now U.S. Pat. No. 3,615,421, and 3,645, filed Jan. 19, 1970 and now U.S. Pat. No. 3,620,724. The reflecting pigment may also be generated in situ as is disclosed in the copending applications of Edwin H. Land, Ser. Nos. 43,741 and 43,742, both filed June 5, 1970 and now U.S. Pat. Nos. 3,647,434 and 3,647,435, respectively.

Particularly preferred integral negative-positive film units contemplated by this invention are those described in the aforementioned U.S. Pat. No. 3,415,644 and which comprise a composite structure containing, as essential layers, in sequence, a dimensionally stable alkali solution impermeable opaque layer, a layer containing a cyan dye developer, a red-sensitive silver halide emulsion layer, a layer containing a magenta dye developer, a green-sensitive silver halide emulsion layer, a layer of yellow dye developer, a blue-sensitive silver halide emulsion layer, a dyeable stratum, a spacer layer, a neutralizing layer and a dimensionally stable alkali solution impermeable transparent layer, the composite structure being employed in combination with a rupturable container retaining an aqueous alkaline processing composition including a white reflecting agent (preferably of the type described in the abovementioned applications which further includes at least one optical filter agent), the container being fixedly positioned and extending along a leading edge of the composite structure so as to be capable of effecting unidirectional discharge of its contents between the dyeable stratum and the blue-sensitive silver halide emulsion layer upon application of compressive pressure. The structural integrity of this film unit may be maintained, at least in part, by the adhesive capacity exhibited between the various layers comprising the laminate at their opposed surfaces. However, such adhesive capacity exhibited at the interface intermediate the dyeable stratum and the next adjacent layer of the negative component should be less than that exhibited at the interface between the opposed surfaces of the remaining layers in order to permit distribution of the processing composition between the dyeable stratum and the next adjacent layer of the negative component as contemplated. The structural integrity may also be enhanced or provided in whole or in part by providing a binding member, e.g., a pressure-sensitive tape as is described with particularity in the aforementioned patents.

In the multicolor systems described above, it is, of course, most desirable to achieve maximal color rendition or accurate color recordation so that the resulting color transfer image most closely approximates in color the subject matter which is being photographed. Such accurate color recordation is dependent upon various factors, one of which is the relative rates or amounts of the dye developers transferred to the positive component to form the color transfer image. Thus the sensitometric design of such a multicolor film unit will be selected to provide specific densities of each of the three dye developers so employed within the prescribed development period in order to achieve optimum color balance and, in turn, most faithful color recordation.

An inherent problem in achieving this objective is the tendency for the dye developer in the set furthest removed from the layer where the processing fluid is applied to be in part delayed by the aforementioned interlayer so that too little of this dye developer is transferred within the prescribed development period. Any attempts to make this interlayer more permeable in turn produce the still moree undesirable effect of backdiffusion of the dye developer in the intermediate set of silver halide emulsion and associated dye developer layer, thereby rendering this approach unacceptable from the standpoint of quality of the resulting color image.

To illustrate this problem further, one type of film unit contemplated by this invention includes a negative component comprising a layer of a phthalocyanine dye developer, a red-sensitive emulsion layer, an interlayer of the type described previously, a layer of magenta dye developer, a green-sensitive emulsion layer, an interlayer as described, a layer of a yellow dye developer, a blue-sensitive emulsion layer and an overlayer of gelatin or the like and which may contain a photographic reagent, e.g., an auxiliary developing agent; and a positive component disposed closest to the overlayer. When the processing fluid is applied between the positive and negative components, there is a tendency for too small an amount of cyan dye developer to be transferred. Attempts to render the first-named interlayer more permeable to permit more ready cyan transfer has been found to result in some back-diffusion of magenta dye developer towards the red-sensitive emulsion layer with the resulting interimage effect by which this back-diffusing magenta dye developer is in part oxidized and hence in part controlled by the red-sensitive (wrong) silver halide emulsion layer and cyan dye developer which should develop this red-sensitive silver halide and hence be immobilized is not and therefore remains soluble and transferable.

In the foregoing discussion, mention was made of magenta back-diffusion and the resulting development of the red-sensitive silver halide emulsion layer by this magenta dye developer, causing loss of magenta dye available for transfer to the positive component. It has also been found that loss of magenta dye or magenta drop-off can be caused by too rapid a forward transfer to the blue-sensitive emulsion before the associated yellow developer has developed developable silver in this layer.-

' It is to these problems that the present invention is directed.

SUMMARY OF THE INVENTION In accordance with the present invention, the firstmentioned problem is materially lessened if not totally obviated by including in the silver halide emulsion furthest removed from the layer of the negative component to which the processing fluid is applied, e.g., the red-sensitive emulsion layer of the last mentioned illustrative negative component, an effective amount of alkali-dissociable inorganic salt; and the aforementioned problem of toorapid forward diffusion of the dye from the middle set of emulsion and associated dye layer may be materially lessened if not totally obviated by including in this middle silver halide emulsion layer an anionic polymeric material such as PVl-IP and an effective amount of alkali-dissociable inorganic salt reactable therewith to prevent this silver halide layer from swelling too rapidly, e.g., to time delay swelling of this layer so that dye may not diffuse through this layer too early in the development process, i.e., until the first silver halide layer is substantially developed. As used herein and in the appended claims, the term effective amount means an amount sufficient to increase appreciably the amount of dye developer transferred within the development period from the associated dye developer layer to the dyeable stratum of the positive component.

DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred film units contemplated by this invention are those described and claimed in the aforementioned U.S. Pat. No. 3,415,644 and referred to in the summary of the invention.

As was mentioned previously, the present invention is directed to those film units employing a negative component comprising a red-sensitive, a greensensitive and a blue-sensitive gelatino silver halide emulsion layer having associated therewith, respectively, a cyan dye developer, a magenta dye developer and a yellow dye developer, each set of silver halide emulsion and associated dye developer being separated from each other set by an interlayer, at least the interlayer furthest removed from the layer where the processing fluid is applied being of the type disclosed above and described and claimed in the aforementioned U.S. Pat. No. 3,625,685; and a positive component including at least a dyeable stratum, which film units are adapted for forming a multicolor diffusion transfer image in the positive component which is viewable, without separation, as a reflection print. Also as was mentioned previously, such film units include means for providing a reflecting agent, such as titanium dioxide, between the positive and negative components in order to mask effectively the negative component and to provide the requisite background for viewing the color transfer image as a positive reflection print. The film units to which this invention is directed preferably also include an acid-reducing or neutralizing layer, e.g., a polymeric acid layer of the type described in U.S. Pat. No. 3,362,819. This neutralizing layer is preferably contained in the positive component on the side of the dyeable stratum opposed from the negative component and most preferably a spacer layer is disposed between the dyeable stratum and this neutralizing layer. Suitable spacer layers are described in the aforementioned U.S. Pat. No. 3,362,819 and in U.S. Pat. Nos. 3,421,893; 3,455,686; 3,575,701 and others. While the neutralizing layer is preferably contained as a layer in the positive component, it may, if desired, be contained in a layer of the negative component as is described, for example, in U.S. Pat. No. 3,573,043. As was also described previously in the background of the invention, the film units preferably also include means for protecting the negative component against fogging so that the film unit may then be developed in the light to form the desired diffusion transfer image.

While the silver halide emulsion layers, dye developer layers and interlayers referred to under the summary of the invention comprise the essential layers of the negative component of this invention, this component may also contain additional layers performing specific desired functions, e.g., the aforementioned neutralizing layer, etc.

The cyan, magenta and yellow dye developers contemplated by this invention are those disclosed in U.S. Pat. Nos. 3,482,972; 3,563,739 and 3,597,200, respectively. While a detailed discussion of these dye developers and illustrative species of each class is not necessary, the following is a brief discussion of these three classes of dye developers which, it will be appreciated, are described with more detail in the aforementioned patents pertaining to them.

The cyan dye developers disclosed in U.S. Pat. No. 3,482,972, which will be referred to in the appended claims simply as phthalocyanine cyan dye developers, may be represented by the formula:

. consisting of aromatic and heterocyclic radicals; Y is a wherein it is provided that of the 16 R substituents present on the phthalocyanine ring at least one or no more than four are as R groups, there being no more than two R groups on any one benzene ring, the remaining R substituents being R groups, wherein R 5 comprises a group (-A),,E; A is a divalent organic linking radical; n is a number of from O to l; E is an aryl group selected from the group consisting of benzene and naphthalene radicals so substituted by at least two groups selected from the group consisting of hydroxyl and amino groups which are situated ortho or para to each other as to be capable of developing an exposed silver halide photographic emulsion; M is a metal se- V lected from the group consisting of cobalt, nickel, copper, chromium, magnesium and zinc; and each R comprises the same or a different moiety selected from the group consisting of monovalent organic and monovalent inorganic radicals, neither of which contain a silver halide developing radical, and hydrogen. Most preferred are those cyan dyes within the above formula wherein the metal moiety is copper and these dye developers may be referred to simply as copper phthalocyanine dye developers.

The magenta dye developers disclosed in US. Pat. No. 3,563,739, which will be referred to hereinafter in .the appended claims as l:l chrome-complexed azo magenta dye developers, may be represented by the formula:

A is an aromatic radical; B is a member of the group radical comprising a silver halide developing substitutent; and Z is a substantially colorless bi-dentate ligand radical.

The yellow dye developers disclosed in US. Pat. No. 3,597,200, which will be referred to hereinafter in the appended claims as 1:1 chrome-complexed azomethine yellow dye developers, may be represented by the formulae:

and

F ll

wherein A is a phenyl or naphthyl radical, B is a phenyl, napthyl or heterocyclic radical, said comprising a radical of an ortho, ortho'-dihydroxy azomethine dye of the formula:

including azomethine dyes wherein at least one of said A and B moieties contains a silver halide developing substituent; X represents the atoms necessary to complete an aliphatic, aromatic or heterocyclic ring, or a derivative thereof containing a radical comprising a silver halide developing substituent; R is alkyl, fluoroalkyl, alkoxy alkyl, phenyl, phenylamino or a radical comprising a silver halide developing substituent, R' is alkyl, alkoxy alkyl, phenyl or phenylamino, R is hydrogen, lower alkyl, phenyl or a radical comprising a silver halide developing substituent, and R is alkyl, hydroxyl, hydrogen or a radical comprising a dihydroxyphenyl silver halide developing substituent, provided that where X represents the atoms necessary to complete an aromatic ring R cannot be hydroxyl and provided further that at least one of said moieties which may contain a silver halide developing substituent does so.

These dye developers are most preferably employed in the respective layers containing them as dispersions in accordance with the disclosure of US. Pat. No. 3,438,775.

As was mentioned previously, the negative interlayers contemplated for use in the film units to which this invention is directed are those described and claimed in US. Pat. No. 3,625,685. Specifically, the interlayer contiguous with the furthest emulsion layer containing the inorganic salt of this invention will comprise such an interlayer and the other interlayer of the negative component may be the same or it may be different, e.g.,

- gelatin, polyvinyl alcohol or any other of the known negative interlayers. However, in the preferred embodiment both of these interlayers comprise interlayers of the type disclosed in the aforementioned patent, e.g., a coalesced essence of an aqueous film-forming polymer dispersion (hereinafter referred to as a latex) and a processing composition permeable material adapted to render the interlayer permeable to soluble dye developer subsequent to contact with the processing composition (hereinafter referred as a permeator). Among the various latex materials disclosed as useful in this copending application are latices of polyvinylidene chloride, lightly carboxylated styrene butadiene copolymers, polyvinyl chloride, vinyl chloridevinyl acetate copolymers, acrylic polymers and copolymers, e.g., a terpolymer of butylacrylate, methylmethacrylate and small amounts of acrylic acid or methacrylic acid, the latices disclosed in U.S. Pat. No. 2,795,564, etc. Preferred latex materials include a 60-38-2 copolymer of methylmethacrylate, butylacrylate and acrylic acid, respectively; a 6030 -4-6 copolymer of butylacrylate, diacetone acrylamide, styrene and methacrylic acid, respectively; and a 60-30-4-6-l.5-0 5 copolymer of butylacrylate, diace tone acrylamide,. styrene, methacrylic acid, 2- sulfoethyl methacrylate and divinyl benzene, respectively, all proportion designations being on a by weight basis. As examples of suitable permeators disclosed in this application, mention may be made of isopropyl cellulose, preferably containing about 1.3 isopropyl groups per cellulosic monomer unit, hydroxypropyl cellulose, acrylonitrile acrylic acid copolymers, methylacrylate acrylic acid copolymers, preferably containing about 3 percent by weight acrylic acid, poly-N-ethyl acrylamide, polyacrylamide, polyethylene oxide, terpolymers of N-ethylacrylamide, methylacrylamide and acrylamide, copolymers of N-ethylacrylamide and 2-vinyl pyridine, copolymers of N-isopropyl acrylamide and N-vinyl pyrrolidone, copolymers of N-isopropyl acrylamide and dimethylaminoethyl acrylate, etc., as well as graft copolymers such as those disclosed in U.S. Pat. No. 3,575,700.

A typical film unit of the foregoing description and to which this invention is directed may, for example,

comprise a cyan dye developer layer containing from about 60 to about 130 mgs./ft. of a phthalocyanine dye developer; a red-sensitive gelatino silver iodobromide emulsion layer containing from about 120 to about 180 mgs./ft. of silver; an interlayer of the foregoing description containing about 150 mgs./ft. of latex and about 5 mgs./ft. of permeator; a layer of magenta dye developer containing from about 70 to about 125 mgs./ft. of a 1:1 chrome-complexed azo magenta dye developer; a green-sensitivegelatino silver iodobromide emulsion layer containing from about 100 to about 130 mgs./ft. of silver; an interlayer containing about 100 mgs./ft. of latex and about 12 mgs./ft. of permeator; a layer containing from about 60 to about 90 mgs/ft. of a 1:1 chrome-complexed azomethine yellow dye developer; a blue-sensitive gelatino silver iodobromide emulsion layer containing from about 100 to about 125 mgs./ft. ofsilver; and an overlayer which may, if desired, contain photographic reagents, e.g., a layer containing about 50 mgs./ft. of gelatin. In addition, any of the aforementioned gelatin-containing layers, e.g., the three silver halide emulsion layers, may contain an anionic polymeric material, the ratio of gelatin to this material being on the order of from about :1 to about 100:1, in accordance with the invention described and claimedin the aforementioned application Ser. No. 78,408 and now U.S. Pat. No. 3,705,798.

While not critical to the practice of this invention, for optimum results the ratios of gelatin to silver in each of the silver halide emulsion layers is important. Best resalts; and the green-sensitive silver halide emulsion layer will contain an anionic polymeric material and an alkali-dissociable inorganic salt or mixture of such salts. The particular amounts or coverages of inorganic salt employed may vary from system to system and accordingly is not readily capable of precise numerical definitions. In general, ratios by weight of inorganic salt to silver in the red-sensitive emulsion layer of from about 1: 10 to about 1:150 may be employed, and ratios of salt to anionic polymeric material, e.g., PVHP, in the green-sensitive silver halide emulsion layer of from about 1:1 to about 1:10 may be employed.

As examples of alkali-dissociable inorganic salts contemplated to be employed in accordance with this invention in the emulsion layer furthest removed from the layer in the negative where the processing fluid is applied, e.g., the red-sensitive silver halide emulsion layer of the film unit illustrated above, mention may be made of nitrates such as potassium, calcium or ammonium nitrate, chlorides such as calcium chloride, as well as other salts which will be readily suggested to those skilled in the art in the light of this disclosure including mixtures thereof.

The beneficial effects of this additive were discovered quite by accident and the theoretical reasons for its behavior in increasing dye transfer are not completely understood. It is believed, however, that it has some effect on the ultimate permeability of the associated latex/permeator interlayer, possibly causing an aggregation of the latex particles into a more porous, open structure. Since this occurs after the overlying (intermediate) emulsion and associated dye developer,

e.g., the green-sensitive emulsion and magenta dye developer of the illustrative and preferred film unit, have been contacted with the developing composition, initiating development and subsequent migration of this dye developer towards the positive component, the back diffusion problem previously discussed, which normally occurs when the interlayer is initially more open to get greater dye density from the furthest dye developer, does not occur. The beneficial results of this additive may also be due, at least in part, to increased development rate caused by its presence and/or to a combination of both of these theoretical considerations. In any event, by way of illustrating the improvements observed by the practice of this invention, in a typical film unit of the type illustrated, cyan dye densities on the order of 1.12 were obtained by including ammonium nitrate in the red-sensitive emulsion layer after imbibition for seconds at room temperature, as compared with cyan densities of from .8 to .9 with control film units under the same conditions with no ammonium nitrate. No magenta drop-off (loss of magenta) was observed.

As examples of alkali-dissociable inorganic salts which may be employed in conjunction with an anionic polymeric material such as PVHP in the intermediate, e.g., the green-sensitive, silver halide emulsion layer, mention may be made of calcium salts such as calcium nitrate and calcium chloride. As was mentioned previously, it is believed that the salt in this emulsion layer reacts in some way with the anionic polymeric material in that layer to prevent the layer from swelling sufficiently to permit forward diffusion of dye developer until the overlying, e.g., blue-sensitive, silver halide emulsion layer is substantially developed by the associated dye developer, e.g., the associated yellow dye developer.

By way of further illustrating the practice of this invention, an integral negative-positive lilm unit of the type described and claimed in U.S. Pat. No. 3,415,644 may be prepared, for example, by coating, in succession, on a gelatin subbed, 4 mil. opaque polyethylene terephthalate film base, the following layers:

1. a layer of cyan dye developer dispersed in gelatin and coated at a coverage of about 75 mgs./ft. of dye and about 80 mgs./ft. of gelatin;

2. a red-sensitive gelatino silver iodobromide emulsion coated at a coverage of about 140 mgs./ft. of silver and about 70 mgs./ft. of gelatin which includes about 1.16 mgs./ft. of potassium nitrate and 0.35 mgs/ft. of calcium chloride hexahydrate;

3. a layer of a 60-30-4-6 copolymer of butylacrylate, diacetone acrylamide, styrene and methacrylic acid and polyacrylamide coated at a coverage of about 150 mgs./ft. of the copolymer and about mgs./ft. of polyacrylamide;

4. a layer of magenta dye developer dispersed in gelatin and coated at a coverage of about 1 l2 mgs./ft. of dye and about 100 mgs./ft. of gelatin;

5. a green-sensitive gelatino silver iodobromide emulsion coated at a coverage of about 100 mgs./ft. of silver and about 50 mgs./ft. of gelatin, and including about 1.40 mgs./ft. of PVHP and about 0.25 mgs/ft. of calcium chloride hexahydrate;

6. a layer containing the copolymer referred to above in layer 3 and polyacrylamide coated at a coverage of about 100 mgs/ft? of copolymer and about 12 mgs/ft. of polyacrylamide;

7. a layer ofyellow dye developer dispersed in gelatin and coated at a coverage of about 73 mgs/ft. of dye and about 56 mgs./ft. of gelatin;

8v blue-sensitive gelatino silver iodobromide emulsion layer including the auxiliary developer 4- methylphenyl hydroquinone coated at a coverage of about 120 mgs./ft. of silver, about 60 mgs./ft. of gelatin and about 30 mgs./ft. of auxiliary developer; and

9. a layer of gelatin coated at a coverage of about 50 mgs./ft. of gelatin.

The three dye developers employed above may be the following:

a magenta dye developer; and

a yellow dye developer.

Then a transparent 4 mil. polyethylene terephthalate film base may be coated, in succession, with the following illustrative layers:

1. a polymeric acid neutralizing layer containing a 7:3 mixture, by weight, of polyethylene/maleic anhydride copolymer and 88-90 percent hydrolyzed polyvinyl acetate at a coverage of about 1000 mgs./ft.

2. a graft copolymer of acrylamide and diacetone acrylamide on a polyvinyl alcohol backbone in a molar ratio of 113.211 at a coverage of about 800 mgs./ft. to

provide a polymeric spacer or timing layer; and

3. a 2:1 mixture, by weight, of polyvinyl alcohol and poly-4-vinylpyridine, at a coverage of about 900 mgs./ft. and including about 20 mgs./ft. of a development restrainer, lphenyl-5-mercaptotetrazole, to provide a polymeric image-receiving layer containing development restrainer.

The two components may then be laminated together to provide the desired integral film unit.

A rupturable container comprising an outer layer of lead foil and an inner liner or layer of polyvinyl chloride retaining an aqueous alkaline processing solution may then be fixedly mounted on the leading edge of each of the laminates, by pressure-sensitive tapes. interconnecting the respective container and laminates so that, upon application of compressive pressure to 0 the container to rupture the containers marginal seal,

its contents may be distributed between the dyeable stratum (layer 3 of the positive component) and the gelatin layer (layer 9) of the negative component.

An illustrative processing composition to be employed in the rupturable container may comprise the following proportions of ingredients:

avalla 1e from Hercules Powder 00., lmlngton, Delaware, under the trade name Natraso1250]. N-phenethyl-a-pleolinlum bromide Benzotrlazole Titanium dioxide 5 H H N N n nHu or! 0H 0 52 gms.

jCu u V (C) 1.18 gms.

' This film unit may then be exposed in known manner to form a developable image and the thus exposed element may then be developed by applying compressive pressure to the rupturable container in order to distribute the aqueous alkaline processing composition, thereby forming a multicolor transfer image which is viewable through the transparent polyethylene terephthalate film base as a positive reflection print. As was heretofore discussed, due to the fact that the negative component is suitably protected from fogging, this development may be effected in the presence of actinic light.

It will be appreciated that the foregoing is by way of illustration only and the various layers of the positive and. negative components may and typically will contain additional reagents performing specific, desired functions 'lhe selection ofthese additional reagents 14 will be readily apparent to those skilled in the art and per se comprises no part of this invention.

As was mentioned previously, the exact reason why the alkali-dissociable inorganic salt provides the improved results heretofore described is not known. It is also not known whether this salt remains in the emulsion layer in which it is initially coated. Possibly it diffuses, at least in part, to one or more other layers of the film unit, e.g., the contiguous interlayer, during or subsequent to formation of the negative component. Accordingly, it is to be expressly understood that any such diffusion or migration is within the spirit of this invention.

In the foregoing description and illustrative examples, reference has been made to employing an alkalidissociable inorganic salt in two of the emulsion layers to obtain, in effect, two separate beneficial results con tributing towards improved color quality of the dye transfer image. It will be appreciated, however, that employment of the salt is but one of these layers will provide beneficial results as compared with a film unit containing no such additive and the invention accordingly contemplates employment of the salt in but one of the silver halide layers to obtain the beneficial results obtainable thereby. i

Since certain changes may be made in the above product without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a photosensitive element including a support having on one side thereof a first light-sensitive silver halide layer having a dye image-providing material associated therewith, a second light-sensitive silver halide layer having a dye image-providing material associated therewith and a third light-sensitive silver halide layer having a dye image-providing material associated therewith at least said first silver halide layer and associated dye image-providing material being separated from said second silver halide layer and associated dye image-providing material by an interlayer comprising a coalesced essence of an aqueous film-forming polymer dispersion which is impermeable to said dye imageproviding material and a processing composition permeable material associated therewith and adapted to render said interlayer permeable to solubilized dye image-forming material subsequent to being contacted with said processing composition;

the improvement which comprises including in said first silver halide layer an effective amount of alkali-dissociable inorganic salt chosen from the group consisting of potassium nitrate, ammonium nitrate, calcium chloride, calcium nitrate or mixtures of these.

2. An element as defined in claim 1, wherein said first silver halide layer comprises a red-sensitive gelatino silver halide emulsion and said associated dye imageproviding material is a cyan dye.

3. An element as defined in claim 2 wherein said second silver halide layer comprises a green-sensitive gelatino silver halide emulsion having a magenta dye image-providing material associated therewith and said green-sensitive gelatino silver halide emulsion layer includes effective amounts of an anionic polymeric mater l and an a is ses ieqr anisalt tiqssn 59m,

the group consisting of calcium chloride, calcium nitrate or mixtures of these.

4. In a photosensitive element comprising, in order,

a layer of a cyan dye developer; a red-sensitive silver halide layer; a first interlayer; a layer of a magenta dye developer; a green-sensitive silver halide layer; a second interlayer; a layer of yellow dye developer; and a blue-sensitive silver halide layer, at least said first interlayer comprising a coalesced essence of an aqueous film-forming polymer dispersion which is impermeable to said cyan dye developer and an alkali permeable macalcium chloride, calcium nitrate or mixtures of these in an amount sufficient to increase materially the amount of said cyan dye developer transferred to said dyeable stratum during said development period.

5. An element as defined in claim 4 wherein said cyan dye developer is a phthalocyanine dye developer.

6. In a photosensitive element comprising, in order, a layer of a phthalocyanine cyan dye developer; a redsensitive gelatino silver iodobromide emulsion layer; a first interlayer; a layer of a 1:1 chrome-complexed azo magenta dye developer; a green-sensitive gelatino silver iodobromide emulsion layer; a second interlayer; a layer of a 1:1 chrome-complexed azomethine yellow dye developer; and a blue-sensitive gelatino silver iodobromide emulsion layer, at least said first interlayer comprising a coalesced essence of an aqueous filmforming polymer dispersion which is impermeable to said cyan dye developer and an alkali permeable material associated therewith and adapted to render said interlayer permeable to said dye developer subsequent to being contacted with an aqueous alkaline processing composition during a predetermined development period to develop said photosensitive element and to impart a color image to a dyeable stratum by diffusion transfer; H

the improvement which comprises including in said red-sensitive silver halide layer alkali-dissociable inorganic salt chosen from the group consisting of potassium nitrate, ammonium nitrate, calcium chloride, calcium nitrate, or mixtures of these in an amount sufficient to increase materially the amount of said cyan dye developer transferred to said dyeable stratum during said development period.

7. An element as defined in claim 6 wherein said green-sensitive gelatino silver iodobromide emulsion layer includes an anionic polymeric material and an effective amount of an alkali-dissociable inorganic salt chosen from the group consiting of calcium chloride, calcium nitrate or a mixture of these.

8. An element as defined in claim 6 wherein said dyeable stratum is disposed in said film unit on the side of said blue-sensitive emulsion layer opposed from said layer of yellow dye developer.

9. A film unit adapted for forming multicolor transfer images comprising:

a negative component comprising a blue-sensitive, a green-sensitive and a red-sensitive gelatino silver halide emulsion having associated therewith in a contiguous layer, respectively, a yellow dye developer, a magenta dye developer and a cyan dye developer, at least said greenand red-sensitive emulsion layers and associated dye developer layers being separated from each other by an interlayer comprising a dye impermeable coalesced essence 10 of an aqueous film-forming polymer dispersion and a processing composition permeable material associated therewith and adapted to render the interlayer permeable to solubilized dye image-forming material subsequent to being contacted with an aqueous alkaline processing composition;

a positive component including at least a dyeable stratum; and

means for providing a reflecting layer between the positive and negative components so that a multicolor transfer image imparted to the dyeable stratum may be viewed as a reflection print without separation of the positive and negative component, which means may comprise a preformed layer disposed between the negative and positive components or a reagent or combination of reagents to be applied to the exposed film unit to provide the reflecting layer;

wherein at least the coating solution employed to provide said red-sensitive silver halide emulsion layer includes an alkali-dissociable inorganic salt ponent in terms of unexposed areas of the assopiaw ,s l eLha iqetarsus a N 10. A film unit as defined in claim 9 wherein said green-sensitive silver halide emulsion layer includes an anionic polymeric material and an alkali-dissociable inorganic salt chosen from the group consisting of calu ch ride i mrn t r i t re qtt nse- 11. A film unit as defined in claim 10 wherein said polymeric material is polyvinyl hydrogen phthalate.

12 l n an integral negative-positive film unit including a negative component comprising at least one lightsensitive silver halide emulsion layer having a dye dev eloper associated therewith; a positive component including at least adyeable stratum; and fiieans for applying a reflecting layer between said positive and negative components in an amount sufficient, upon development of said film unit, to mask effectively said negative component and to provide a background for viewing a color transfer image imparted to said dyeable stratum of said positive component by reflected light; the

irngqgqmept which comprises employing as said m negative component an element as defined in claim 1 composition to develop said filmun t-H 14. A film unit as defined in claim 13 wherein said processir g composition includes a reflecting agent.

' 15. A film unit as defined in claim l 2 vvherein said 16. A photographic film unit which comprises, in

combination:

a photosensitive element including a composite structure containing, as essential layers, in sequence, a dimensionally stable alkaline solution impermeable opaque layer; a layer of a phthalocyanine dye developer; a red-sensitive gelatino silver iodobromide emulsion layer containing an effective amount of alkali-dissociable inorganic salt chosen from the group consisting of potassium nitrate, ammonium nitrate, calcium chloride, calcium nitrate or mixtures of these; a first spacer layer comprising a coalesced essence of an aqueous film-forming polymer dispersion which is impermeable to said cyan dye developer and an alkali permeable material associated therewith and adapted to render said spacer layer permeable to said dye developer subsequent to being contacted with an aqueous alkaline processing composition; a layer of a magenta dye developer; a green-sensitive gelatino silver iodobromide emulsion layer including an effective amount of polyvinyl hydrogen phthalate and an alkali-dissociable inorganic salt chosen from the group consisting of calcium chloride, calcium nitrate or a mixture of these; a second spacer layer; a layer of a yellow dye developer; a bluesensitive gelatino silver iodobromide emulsion layer; a third spacer layer; a dyeable stratum; a polymeric acid layer containing sufficient acidifying groups to effect reduction of a processing solution having a first pH at which said dye developers are soluble and diffusible to asecond pH at which said dye developers are substantially insoluble and non-diffusible; a dimensionally stable alkaline solution impermeable transparent layer; means securing at least the side edges of said opposed layers in fixed relationship; and a rupturable container retaining an aqueous alkaline processing solution having said first pH and containing dispersed therein a white inorganic pigment in a quantity sufficient to mask effectively said silver halide layers and any dye developer associated therewith after development and to provide a background for viewing a diffusion transfer image formed by development of said film unit, by reflected light, through said transparent layer, said rupturable container being fixedly positioned and extending transverse a leading edge of said photosensitive element so as to be capable of effecting unidirectional discharge of the containers contents between said dyeable stratum and said third spacer layer upon application of compressive force to said container.

17. A film unit as defined in claim 16 wherein said oper subsequent to being contacted with an aqueous alkaline processing composition.

18. A film unit as defined in claim 17 wherein said magenta dye developer comprises a 1:1 chromecomplexed azo dye developer and said yellow dye developer comprises a 1:1 chrome-complexed azomethine dye developer.

19. A film unit a defined in claim 18 wherein said third spacer layer comprises gelatin and said film unit further includes a timing layer disposed between said dyeable stratum and said polymeric acid layer.

20. A photographic film unit which comprises, in combination:

a photosensitive element including a composite structure containing, as essential layers, in sequence, a dimensionally stable alkaline solution impermeable opaque layer; a layer of a phthalocyanine dye developer; a red-sensitive gelatino silver iodobromide emulsion layer containing an effective amount of alkali-dissociable inorganic salt chosen from the group consisting of potassium nitrate, ammonium nitrate, calcium chloride or a mixture of these; a first spacer layer comprising a coalesced essence of an aqueous film-forming polymer dispersion which is impermeable to said cyan dye developer and an alkali permeable material associated therewith and adapted to render said spacer layer permeable to said dye developer subsequent to being contacted with an aqueous alkaline processing composition; a layer of a magenta dye developer comprising a 1:1 chrome complexed azo dye developer; a green-sensitive gelatino silver iodobromide emulsion layer including an effective amount of polyvinyl hydrogen phthalate and an alkali-dissociable inorganic salt chosen from the group consisting of calcium chloride, calcium nitrate or a mixture of these; a second spacer layer; a layer of a yellow dye developer comprising a 1:1 chrome complexed azomethine dye developer; a blue-sensitive gelatino silver iodobromide emulsion layer; a third spacer layer; a dyeable stratum; a polymeric acid layer containing sufficient acidifying groups to effect reduction of a processing solution having a first pH at which said dye developers are soluble and diffusible to a second pH at which said dye developers are substantially insoluble and non-diffusible; a dimensionally stable alkaline solution impermeable transparent layer; means securing at least the side edges of said opposed layers in fixed relationship; and a rupturable container retaining an aqueous alkaline processing solution having said first pH and containing dispersed therein a white inorganic pigment in a quantity sufficient to mask effectively said silver halide layers and any dye developer associated therewith after development and to provide a background for viewing a diffusion transfer image formed by development of said film unit, by reflected light, through said transparent layer, said rupturable container being fixedly positioned and extending transverse a leading edge of said photosensitive element so as to be capable of effecting unidirectional discharge of the containers contents between said dyeable stratum and said third spacer layer upon application of compressive force to said container. 

2. An element as defined in claim 1, wherein said first silver halide layer comprises a red-sensitive gelatino silver halide emulsion and said associated dye image-providing material is a cyan dye.
 3. An element as defined in claim 2 wherein said second silver halide layer comprises a green-sensitive gelatino silver halide emulsion having a magenta dye image-providing material associated therewith and said green-sensitive gelatino silver halide emulsion layer includes effective amounts of an anionic polymeric material and an alkali-dissociable inorganic salt chosen from the group consisting of calcium chloride, calcium nitrate or mixtures of these.
 4. In a photosensitive element comprising, in order, a layer of a cyan dye developer; a red-sensitive silver halide layer; a first interlayer; a layer of a magenta dye developer; a green-sensitive silver halide layer; a second interlayer; a layer of yellow dye developer; and a blue-seNsitive silver halide layer, at least said first interlayer comprising a coalesced essence of an aqueous film-forming polymer dispersion which is impermeable to said cyan dye developer and an alkali permeable material associated therewith and adapted to render said interlayer permeable to said dye developer subsequent to being contacted with an aqueous alkaline processing composition during a predetermined development period to develop said photosensitive element and to impart a color image to a dyeable stratum by diffusion transfer; the improvement which comprises including in said red-sensitive silver halide layer an alkali-dissociable inorganic salt chosen from the group consisting of potassium nitrate, ammonium nitrate, calcium chloride, calcium nitrate or mixtures of these in an amount sufficient to increase materially the amount of said cyan dye developer transferred to said dyeable stratum during said development period.
 5. An element as defined in claim 4 wherein said cyan dye developer is a phthalocyanine dye developer.
 6. In a photosensitive element comprising, in order, a layer of a phthalocyanine cyan dye developer; a red-sensitive gelatino silver iodobromide emulsion layer; a first interlayer; a layer of a 1:1 chrome-complexed azo magenta dye developer; a green-sensitive gelatino silver iodobromide emulsion layer; a second interlayer; a layer of a 1:1 chrome-complexed azomethine yellow dye developer; and a blue-sensitive gelatino silver iodobromide emulsion layer, at least said first interlayer comprising a coalesced essence of an aqueous film-forming polymer dispersion which is impermeable to said cyan dye developer and an alkali permeable material associated therewith and adapted to render said interlayer permeable to said dye developer subsequent to being contacted with an aqueous alkaline processing composition during a predetermined development period to develop said photosensitive element and to impart a color image to a dyeable stratum by diffusion transfer; the improvement which comprises including in said red-sensitive silver halide layer alkali-dissociable inorganic salt chosen from the group consisting of potassium nitrate, ammonium nitrate, calcium chloride, calcium nitrate, or mixtures of these in an amount sufficient to increase materially the amount of said cyan dye developer transferred to said dyeable stratum during said development period.
 7. An element as defined in claim 6 wherein said green-sensitive gelatino silver iodobromide emulsion layer includes an anionic polymeric material and an effective amount of an alkali-dissociable inorganic salt chosen from the group consiting of calcium chloride, calcium nitrate or a mixture of these.
 8. An element as defined in claim 6 wherein said dyeable stratum is disposed in said film unit on the side of said blue-sensitive emulsion layer opposed from said layer of yellow dye developer.
 9. A film unit adapted for forming multicolor transfer images comprising: a negative component comprising a blue-sensitive, a green-sensitive and a red-sensitive gelatino silver halide emulsion having associated therewith in a contiguous layer, respectively, a yellow dye developer, a magenta dye developer and a cyan dye developer, at least said green- and red-sensitive emulsion layers and associated dye developer layers being separated from each other by an interlayer comprising a dye impermeable coalesced essence of an aqueous film-forming polymer dispersion and a processing composition permeable material associated therewith and adapted to render the interlayer permeable to solubilized dye image-forming material subsequent to being contacted with an aqueous alkaline processing composition; a positive component including at least a dyeable stratum; and means for providing a reflecting layer between the positive and negative components so that a multicolor transfer image imparted to the dyeable stratum may be viewed as a reflection print without separation of the positive and negative component, which means may comprise a preformed layer disposed between the negative and positive components or a reagent or combination of reagents to be applied to the exposed film unit to provide the reflecting layer; wherein at least the coating solution employed to provide said red-sensitive silver halide emulsion layer includes an alkali-dissociable inorganic salt chosen from the group consisting of potassium nitrate, ammonium nitrate, calcium chloride, calcium nitrate or mixtures of these to obtain greater transfer of the associated dye to the positive component in terms of unexposed areas of the associated silver halide layer.
 10. A film unit as defined in claim 9 wherein said green-sensitive silver halide emulsion layer includes an anionic polymeric material and an alkali-dissociable inorganic salt chosen from the group consisting of calcium chloride, calcium nitrate or mixtures of these.
 11. A film unit as defined in claim 10 wherein said polymeric material is polyvinyl hydrogen phthalate.
 12. In an integral negative-positive film unit including a negative component comprising at least one light-sensitive silver halide emulsion layer having a dye developer associated therewith; a positive component including at least a dyeable stratum; and means for applying a reflecting layer between said positive and negative components in an amount sufficient, upon development of said film unit, to mask effectively said negative component and to provide a background for viewing a color transfer image imparted to said dyeable stratum of said positive component by reflected light; the improvement which comprises employing as said negative component an element as defined in claim
 1. 13. A film unit as defined in claim 12 including means for applying an aqueous alkaline processing composition to develop said film unit.
 14. A film unit as defined in claim 13 wherein said processing composition includes a reflecting agent.
 15. A film unit as defined in claim 12 wherein said negative and positive components are confined between a pair of support members, at least the support member associated with the positive component being transparent.
 16. A photographic film unit which comprises, in combination: a photosensitive element including a composite structure containing, as essential layers, in sequence, a dimensionally stable alkaline solution impermeable opaque layer; a layer of a phthalocyanine dye developer; a red-sensitive gelatino silver iodobromide emulsion layer containing an effective amount of alkali-dissociable inorganic salt chosen from the group consisting of potassium nitrate, ammonium nitrate, calcium chloride, calcium nitrate or mixtures of these; a first spacer layer comprising a coalesced essence of an aqueous film-forming polymer dispersion which is impermeable to said cyan dye developer and an alkali permeable material associated therewith and adapted to render said spacer layer permeable to said dye developer subsequent to being contacted with an aqueous alkaline processing composition; a layer of a magenta dye developer; a green-sensitive gelatino silver iodobromide emulsion layer including an effective amount of polyvinyl hydrogen phthalate and an alkali-dissociable inorganic salt chosen from the group consisting of calcium chloride, calcium nitrate or a mixture of these; a second spacer layer; a layer of a yellow dye developer; a blue-sensitive gelatino silver iodobromide emulsion layer; a third spacer layer; a dyeable stratum; a polymeric acid layer containing sufficient acidifying groups to effect reduction of a processing solution having a first pH at which said dye developers are soluble and diffusible to a second pH at which said dye developers are substantially insoluble and non-diffusible; a dimensionally stable alkaline solution impermeable transparent layer; means securing at least the side edges of said opposed layers in fixed relationship; and a rupturable container retaining an aqueous alkaline Processing solution having said first pH and containing dispersed therein a white inorganic pigment in a quantity sufficient to mask effectively said silver halide layers and any dye developer associated therewith after development and to provide a background for viewing a diffusion transfer image formed by development of said film unit, by reflected light, through said transparent layer, said rupturable container being fixedly positioned and extending transverse a leading edge of said photosensitive element so as to be capable of effecting unidirectional discharge of the container''s contents between said dyeable stratum and said third spacer layer upon application of compressive force to said container.
 17. A film unit as defined in claim 16 wherein said second spacer layer also comprises a dye impermeable coalesced essence of an aqueous film-forming polymer dispersion and a processing composition permeable material associated therewith and adapted to render said spacer layer permeable to solubilized dye developer subsequent to being contacted with an aqueous alkaline processing composition.
 18. A film unit as defined in claim 17 wherein said magenta dye developer comprises a 1:1 chrome-complexed azo dye developer and said yellow dye developer comprises a 1:1 chrome-complexed azomethine dye developer.
 19. A film unit a defined in claim 18 wherein said third spacer layer comprises gelatin and said film unit further includes a timing layer disposed between said dyeable stratum and said polymeric acid layer.
 20. A photographic film unit which comprises, in combination: a photosensitive element including a composite structure containing, as essential layers, in sequence, a dimensionally stable alkaline solution impermeable opaque layer; a layer of a phthalocyanine dye developer; a red-sensitive gelatino silver iodobromide emulsion layer containing an effective amount of alkali-dissociable inorganic salt chosen from the group consisting of potassium nitrate, ammonium nitrate, calcium chloride or a mixture of these; a first spacer layer comprising a coalesced essence of an aqueous film-forming polymer dispersion which is impermeable to said cyan dye developer and an alkali permeable material associated therewith and adapted to render said spacer layer permeable to said dye developer subsequent to being contacted with an aqueous alkaline processing composition; a layer of a magenta dye developer comprising a 1:1 chrome complexed azo dye developer; a green-sensitive gelatino silver iodobromide emulsion layer including an effective amount of polyvinyl hydrogen phthalate and an alkali-dissociable inorganic salt chosen from the group consisting of calcium chloride, calcium nitrate or a mixture of these; a second spacer layer; a layer of a yellow dye developer comprising a 1:1 chrome complexed azomethine dye developer; a blue-sensitive gelatino silver iodobromide emulsion layer; a third spacer layer; a dyeable stratum; a polymeric acid layer containing sufficient acidifying groups to effect reduction of a processing solution having a first pH at which said dye developers are soluble and diffusible to a second pH at which said dye developers are substantially insoluble and non-diffusible; a dimensionally stable alkaline solution impermeable transparent layer; means securing at least the side edges of said opposed layers in fixed relationship; and a rupturable container retaining an aqueous alkaline processing solution having said first pH and containing dispersed therein a white inorganic pigment in a quantity sufficient to mask effectively said silver halide layers and any dye developer associated therewith after development and to provide a background for viewing a diffusion transfer image formed by development of said film unit, by reflected light, through said transparent layer, said rupturable container being fixedly positioned and extending transverse a leading edge of said photosensitive element so as to be capable of effecting uNidirectional discharge of the container''s contents between said dyeable stratum and said third spacer layer upon application of compressive force to said container. 